In vehicles having multiple drive axles, such as vehicles having full-time or automatic all-wheel drive (AWD) transmissions, the wheels on one drive axle at times must rotate or spin at a different relative speed than the wheels on the other drive axle in order to limit slippage due to poor traction at the road interface near one or more tires, such as when the vehicle passes over a patch of ice. Also, at times a wheel on one side of a drive axle of an AWD, front-wheel, or rear-wheel drive vehicle might need to rotate or spin at a different rate from that of the wheel disposed on the other side of the same drive axle, such as when the vehicle is turning.
To enable such disparate wheel rotational speeds, a coupling device known as a differential is commonly employed to divide torque from the engine and distribute or apportion the torque at two ends of a single drive axle or between multiple drive axles. Differential gears typically include a drive shaft that rotates a housing containing two or more planetary bevel gears, one on each of the driven shafts. The meshed bevel gears cause the sum of the rotation rates of the driven shafts to be held constant, although one bevel gear may rotate at a different rate than the other. However, bevel gears tend to be heavy, and the manufacture of limited slip differentials (LSDs) containing bevel gears is therefore relatively expensive. As a result, systems having such gear designs, including LSDs having add-ons such as multi-disk and/or viscous coupling, tend to carry a cost premium, and may be less than optimal in terms of size, weight, and smoothness of function.